Add de-emph filter

1 files changed, 4 insertions, 0 deletions

diff --git a/async_fm_demod.py b/async_fm_demod.py
index d2289e4..8b4aa9e 100644
--- a/async_fm_demod.py
+++ b/async_fm_demod.py
@@ -17,6 +17,10 @@ async def streaming():
         samples = np.array(samples).astype('complex64')
         samples = signal.decimate(samples, int(1.2e6 / 200e3))
         samples = np.angle(samples[1:] * np.conj(samples[:-1]))
+
+        x = np.exp(-1 / (200e3 * 75e-6))
+        samples = signal.lfilter([1-x], [1,-x], samples)
+
         samples = signal.decimate(samples, int(200e3 / 50e3))
         samples *= 10000